Personalised Cancer Vaccine Cuts Risk of Melanoma Spreading by 38% in Major Clinical Trial

A personalised cancer vaccine developed through a collaboration between Moderna and Merck has shown promising results in a major international clinical trial, reducing the risk of melanoma spreading to distant parts of the body or causing death by 38% when combined with an existing immunotherapy treatment.

The experimental treatment, known as intismeran autogene, was evaluated in patients with high-risk melanoma whose tumours had been surgically removed. The findings offer fresh evidence that treatments tailored to the genetic characteristics of an individual’s cancer could improve outcomes after surgery.

The Phase 3 trial involved 1,137 patients and compared the personalised vaccine combined with pembrolizumab, an immunotherapy drug sold as Keytruda, against pembrolizumab alone. Researchers reported that the combination also reduced the risk of cancer recurrence or death by 42%.

Although the results represent a significant development in personalised cancer treatment, the vaccine remains investigational and is not yet approved for routine clinical use.

How the Personalised Cancer Vaccine Works

Unlike conventional preventive vaccines, which aim to protect people from infections before they occur, this treatment is designed for patients who have already been diagnosed with cancer.

Every tumour develops a distinct collection of genetic changes. Some of these changes produce abnormal proteins called neoantigens, which can help distinguish cancer cells from healthy tissue.

To develop the personalised vaccine, researchers analyse a sample of a patient's tumour and identify suitable cancer-specific targets. Scientists then use messenger RNA (mRNA) technology to create a treatment that instructs the body's cells to present these targets to the immune system.

This process is intended to train immune cells, particularly T cells, to recognise and attack cancer cells carrying the selected markers. The goal is to help eliminate microscopic cancer cells that may remain after surgery, even when the visible tumour has been removed.

Because the vaccine is designed around each patient's tumour, its composition differs from one individual to another.

Immunotherapy Helps Strengthen the Immune Response

The vaccine is administered alongside pembrolizumab, an established immunotherapy that works through a different mechanism.

Cancer cells can exploit immune checkpoints, which normally help prevent the immune system from attacking healthy tissue. Pembrolizumab blocks the PD-1 checkpoint pathway, helping immune cells maintain their ability to recognise and attack cancer.

The personalised vaccine provides more specific targets for the immune system, while pembrolizumab helps support the resulting immune response.

Researchers are investigating whether combining these approaches can improve the chances of keeping high-risk patients cancer-free following surgery.

What the Clinical Trial Found

The international INTerpath-001 trial included patients with high-risk stage IIB to stage IV melanoma whose tumours had been surgically removed.

After two years, approximately 82.2% of patients who received the vaccine alongside pembrolizumab remained free from cancer recurrence, compared with 70% of those who received pembrolizumab alone.

The results indicate an absolute difference of 12.2 percentage points between the groups in recurrence-free outcomes at the two-year mark.

The combination also reduced the relative risk of distant metastasis or death by 38% compared with immunotherapy alone. Distant metastasis refers to cancer spreading from its original location to other parts of the body.

These findings are encouraging, but they do not mean that the vaccine eliminates cancer risk or guarantees recovery for every patient. Researchers will need longer follow-up to determine whether the improvement in recurrence-related outcomes translates into better overall survival.

Side Effects and Access Remain Important Questions

The treatment was generally reported to be manageable, with vaccine-related effects including injection-site pain, headaches and chills. Pembrolizumab can also cause immune-related side effects, some of which may be serious.

Personalised treatment presents practical challenges as well. Each vaccine requires tumour analysis, genetic sequencing and specialised manufacturing, which could affect production time, availability and cost.

The results were presented at the European Society for Medical Oncology Congress in October 2026. The developers are pursuing regulatory discussions, but approval will require further review by the relevant authorities.

Could the Technology Be Used Against Other Cancers?

Researchers are also studying personalised cancer vaccines in other tumour types, including kidney, bladder and lung cancers. However, the melanoma findings cannot automatically be applied to these diseases, and separate clinical evidence will be needed.

For now, the trial provides strong evidence that matching a treatment to the unique characteristics of an individual's tumour can improve outcomes for a defined group of melanoma patients. Further research will determine the treatment's long-term benefits, affordability and potential role in cancer care.